Adjustable magnet for a magnetron



Jan. 24, 1967 BESSARAB 3,300,681

ADJUSTABLE MAGNET FOR A MAGNETRON Original Filed April 2'7, 1962 -FIG.I.-

INVENTORI MICHAEL BESSARAB,

W -25 1; BY 2118 ATTORNE United States Patent 3,300,681 ADJUSTABLE MAGNET FOR A MAGNETRON Michael Bessarab, Scotia, N.Y., assignor to General Electric Company, a corporation of New York Continuation of application Ser. No. 190,753, Apr. 27, 1962. This application Oct. 22, 1965', Ser. No. 506,901

6 Claims. (Cl. 315-"39.71)

This application is acontinuationofapplication Serial No. 190,753, filed April 27, 1962, now abandoned, and assigned to the same assignee-as the present invention.

My invention relates to radio frequency apparatus and pertains more particularly to improved volt-age tunable magnetron packages and improved means adapted for adjustably varying the;.configur ation of operating magnetic fields required to extend generally'coaxially through voltage tunable magnetron tubes incorporated in such packages. I

A voltage tunable magnetron package generally comprises an RF. circuit having an RF. output and a voltage tunable magnetron tube mounted in the RF. circuit, D.C. circuit means for applying appropriate operating potentials to the electrodes of the tube and a magnet assembly. The tube usually includes electrode elements defining an interaction region and an axially displaced electron injection system for directing electrons axially in a con trolled manner into the interaction region. The magnet assembly generally includes a permanent magnet having closely. spaced opposed pole pieces defining a gap and means for mounting the magnetron tube and circuit means in a predetermined position in which the magnetic field in-the gap extends generally coaxially through the magnetron tube.

Usually the generally coaxial relation of magnetron tube and magnetic field can be relatively easily obtained and maintained through the use of adjusting fixtures and means for affixing the RF. circuitry containing the tube to the magnet assembly in a predetermined adjusted position. However, variations in magnet flux concentration at discrete points across the faces of the magnet pole pieces or slight misalignments of the tube parts, and particularly the parts comprising the electron injection system, resulting during tube assembly can adversely affect tube operating characteristics, such as power output, and operating efiiciency. In order to compensate for such magnet flux variations and slight tube misalignments it is desirable to provide means for enabling, where required, some form of vernier, or fine, adjustment to the general adjustment whereby the tubes are generally coaxially aligned relative to the magnetic fieldl" My invention contemplates the provision of improved voltage tunable magnetron packages including means adapted for enabling variations of the configuration of the magnetic field in the gap and thus obtaining the desired vernier adjustment without disturbing the general adjustment orrequiring movement of the tube and tube circuitry. More specifically, my invention contemplates the provision of improved structure wherein the gap-defining inner surfaces of the pole pieces are adjustable to assume various angular positions, thereby, to determine, and enable adjustive variations of, the configuration of the magnetic field therebetween. In one form of my invention the pole pieces are mounted on the yoke section of the magnet structure with a universal ball-and-socketlike arrangement enabling independent tilting of each of the mentioned gap-defining surfaces to various angles. Another form of my invention contemplates the provision of pole pieces having tapered cross sections and which are each relatively rotatable to enable positioning of the gapdefining surfaces in various oblique planes relative to the tube axis.

Accordingly, a primary object of my invention is to 3,360,681 Patented Jan. 24, 1967 provide a new and improved voltage tunable magnetron package including new and improved means for effecting relative adjustment of the magnetic field and the tube contained therein.

Another object of my invention is to provide new and improved means for obtaining adjustable variations of the configuration of the magnetic field extending generally coaxially through the magnetron tube in a voltage tunable magnetron package, thereby to enhance tube operation.

Another object of my invention is to provide new and improved means enabling fixed mounting of the tube of a voltage tunable magnetron package in a general adjusted position and a vernier adjustment of the general adjustment.

- Another object of my invention is to provide a new and improved voltage tunable magnetron package including new and improved magnet gap-defining means adapted for providing predeterminedly-shaped fields in the gaps and thereby effective to compensate for flux variations in the discrete regions across the gap-defining surfaces or for the undesirable effects of misalignment of parts in the magnetron tube included in the package.

Another object of my invention is to provide new and improved magnet structures including new and improved means for adjustably varying the configuration of the magnetic fields in the gap regions thereof.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of my invention I provide a unitary package assembly including a magnet having a yoke section including a pair of pole regions each of which is provided with a movable pole piece. The pole pieces include opposed surfaces defining a gap having a voltage tunable magnetron tube positioned therein. The tube comprises an envelope containing a non-emissive cathode and a surrounding anode circuit defining therewith an interaction region and an electron injection system including an emissive cathode, all axially arranged with the injection system axially spaced from the interaction region and adapted for controlled direction of electrons into the interaction region. Additionally, the tube is securely mounted in an RF. circuit and includes an axially-spaced pair of anode contacts making conductive contact with opposed walls of the cavity circuit. The cavity circuit is rigidly mounted relative to the magnet and in such a generally adjusted position as to position the tube therein in general coaxial relation with the magnetic field in the gap. In one form of my invention the mentioned movable pole pieces are mounted by means of universal joints whereby each pole piece can be indepcndently tilted to various positions. Thus, the opposed gap-defining surfaces of the pole pieces can extend in various relative planes for thereby determining the configuration of the magnetic field in the gap and enabling a vernier adjustment of the relation of the field and tube. According to another form of my invention, the pole pieces can each comprise a disk-like element l'otatively mounted on the magnet yoke and having a tapeerd crosssection. Thus, the oppoesd inner surfaces of the pole pieces which define the gap having the tube mounted therein and the configuration of the field in the gap can be varied by relatively rotating the pole pieces and thereby providing vernier adjustment of the relation of the field and the tube.

For a better understanding of my invention, reference may be had to the accompanying drawing'in which:

' FIG. 1 is a partially 'sectionalized view of an embodiment of my invention;

the same assignee as the present invention.

FIG. 2 is a fragmentary and partially sectionalized view of a modified form of my invention; and

FIG. 3 is a fragmentary view of another modified form of my invention.

Referring'to FIG. 1, there is shown a voltage tunable magnetron package generally designated land embodying a form of my invention. The package 1 comprises a so-called permanent E magnet which includes a yoke section having a pair of opposed pole-supporting regions generally designated N and 'S. From the outset, it is to be understood that my invention is not limited to structures employing the particular form of magnet herein disclosed but is applicable to structures including other types of magnets such, for example, as the so-called C magnets.

Provided on each of the pole regions N and S is a separate movable pole piece 3. In the present embodiment the pole pieces 3 are preferably formed of a high-permeability magnetic material and to include opposed spaced planar and coextensive surfaces 4 which are appropriately spaced and cooperate to define an unobstructed magnet gap. Additionally, each pole piece includes a convex outer surface 5 positioned in a concave recess 6 formed in the adjacent one of the pole regions N and S. The surfaces 5 and 6 cooperate to provide what might be termed universal, or ball-and-socket-type, joints which are adapted for enabling the pole pieces 3 to be moved to various adjustive positions in which the surfaces 4 extend at various oblique angles relative to the axis of the field therebetween. The pole pieces can be held in these adjusted positions initially by magnetic attraction and can subsequently be locked in such positions either by a bonding material, such as that indicated by 7, or by any other suitable fastening or bonding means. Potting compounds and solder materials have been effectively employed for making the bonds 7.

Through adjustable positioning of the pole pieces 3 the configuration of the field extending between the planar surfaces 4 defining the magnet gap can be adjustably varied. The advantages flowing from this capability of the structure will be more fully discussed hereinafter.

Mounted in the magnet structure 2 and comprising a subassembly of the package is an R.F. cavity circuit 8. The cavity circuit 8 can be of the reentrant type and has mounted therein a voltage tunable magnetron tube generally designated 10 and which can be of the type disclosed and claimed in US. Patent No. 2,930,933 of G. I. Grifiin, Jr., et al. issued March 29, 1960 and assigned to Briefly, and as illustrated in FIG. 1, the magnetron 10 is constructed to include alternate ceramic and metal elements. The ceramic elements generally include a plurality of cylindrical ceramic wall sections 11 and an apertured disk-like ceramic end cap 12. The metal members are suitably brazed to or between oppose-d surfaces of the ceramic elements to complete a hermetically sealed evacuated envelope and include a metal end cap 13 carrying a cylindrical nonemissive cathode 14 extending centrally in a cylindrical space defined by a plurality of anode segments generally designated 15. The anode segments 15 are arranged in a pair of interdigital sets with each segment being carried by a washer-like anode contact ring 16. The rings 16 are sealed between a pair of the ceramic cylinders 11 and are thus mutually insulated. A filamentary emitter 17 is suitably mounted on the ceramic end cap 12 with leads sealed therethrough and connected to a pair of button-like contact members 18 bonded to the outer surface of the ceramic end cap. A frustoconical control electrode 19 is sealed between one of the ceramic insulators 11 and the ceramic end cap 12 and is positioned about the emitter 17. By means of a lead not shown and which extends also in a sealed manner through the ceramic end cap 12, an electrical connection is made between the control electrode 19 and another buttonvlike contact member 20 bonded to the outer surface of the ceramic end cap. Suitable D.C. leads (not shown) are provided for connecting to the contacts 17, 18 and 20 and providing suitable operating potentials on the various described electrodes to provide for voltage tuning and power control through the control of electron injection into the interaction region defined by the nonemissive cathode "14 and the anode circuit defined by the seg-. ments 15.

The tube 10 is positioned in the cavity circuit 8 with the lower-anode contactin an annular shoulder formed on the rim of an aperture in.a ,reentrant section of the cavity and with the lower end of the tube protruding through the aperture to enable access for making mentioned D.C. connections to the contacts 18 and 20. The tube is secured in the shown position by a threaded retaining ring 21 which engages the upper one of the anode contacts 16 and is-threaded in the upper side of the cavity with the upper end of the tube protruding therethrough to provide access for making a DC. connection to the nonemissive cathode 14 through themetal end cap 13. Thusly, the tube is securely retained in the cavity with the anode contacts 16 making appropriate conductive contact with opposed sides of the cavity to adapt the cavity walls to serve as an inductance in completing an oscillatory circuit including the cavity inductance and the capacitance afforded by the interdigitally arranged anode segments 15. p

The magnetron tube 10 is adapted for operating while axially aligned with a magnetic field. Thus, the cavity circuit "8 with the tube 10 mounted therein is supported with the tube positioned in the gap defined by the pole pieces 3. The circuit 8 can be supported directly by the magnet structure 2 by means of brackets 22 or any suitable means for holding the circuit and tube in a fixed position in the gap. Prior to securing the circuit in place the circuit with the tube therein is, with the aid of appropriate fixtures, adjustively manipulated to provide for a generally coaxial adjusted alignment of the tube and the magnet field in the gap with the planar surfaces 4 extending parallel to each other and perpendicular to the tube axis. The cavity circuit is then secured to the magnet structure to maintain the adjusted generally coaxial relationship of tube axis and magnetic field. Subsequently, a Vernier, or fine, adjustment of the relative positions of the magnetic field and tube axis can be effected by adjustively manipulating the movable pole pieces 3. Specificallly, should it'ap-pear that the tube characteristics, such as power output, or operating efliciency are not optimum due to some variations in field strength across the gap or'due tosome slight misalignment of tube parts, corrective or compensating adjustment can be made by tilting thepole pieces} in their ball, or universal, sockets. In this manner the opposed planar gap-defining surfaces 4 on the pole pieces Scan be positioned in various parallel or non-parallel planes for varying the configuration of the field or rotating the field about its axis. Thus, it is possible to provide adjustment of the relative position of the 'field and-tube axis to optimize tube operation and efficiency and without disturbing the general adjustment effected when the cavity is secured in position in the magnet structure. I

Illustrated in FIG. 2 is a modified form of my invention which can be identical in all respects to the structure of FIG. 1 except for the mounting of the movable pole pieces. In the embodiment of FIG. 2 movable pole pieces 25 include opposed planar surfaces 26 defining a gap wherein a magnetron tube 10 in a cavity circuit 8 is mounted and concave surfaces 27 in the pole pieces mate with convex surfaces 28 formed on the opposedpole regions N and S of the magnetron. This is the reverse form of the universal, or ball-and-socket-type, joints illustrated in FIG. 1 but is elfective for enabling the same adjustable manipulation or tilting of the-pole pieces for varying the positions of the planar surfaces 26 to vary the magnetic field configuration and position in the gap. In this embodiment also the pole pieces can be held in a desired adjusted position by bonding, such as that indicated at 29, or by any other suitable securing means.

Another embodiment of my invention is illustrated in FIG. 3.v In this embodiment the structure can be substantially identical to that of FIG. 1 except for the type of movable pole pieces provided. Specifically, in this embodiment the pole region N is formed with upper and lower, surfaces 30 and 31, respectively, which are parallel to each other and also to respective surfaces 32 and 33 on pole region S. Also, thepole regions N and S are formed with coaxial bores in which are positioned rotatable stems 34. Secured on the inner ends of the stems 34 and slidably rotatable on the surfaces 31 and 32 are opposed pole pieces 35. Each pole pieces 35 is tapered in cross-section to provide a planar surface 36 which is oblique relative to the axis of a magnetron tube mounted in a cavity 8 and positioned in the gap defined by the opposed surfaces 36. As seen in the drawing, the pole pieces 35 can each be angulared to assist in concentrating the ends of the field on the surfaces 36. Fitted securely on the outer end of each stem 34 is an adjusting knob 37 which can have a knurled rim to facilitate turning and can be furnished with a screw 38, or the like, adapted for securing the arrangement in any desired rotative adjusted position.

By turning the adjusting knob 37 each pole piece 35 can be independently rotated to cause the surface thereof to assume various adjusted planar positions, which in cooperation with, or depending upon the position of, the surface 36lon the opposite pole piece will determine the configuration and rotative positionof the magnetic field extendingQgenerally coaxially through the tube 10. In this manner it is possible to provide a vernier, or fine, adjustment of the initial adjustment effected when the cavity issecured to the magnet and whereby the mentioned general adjustment is obtained.

It is to be understood from the foregoing that While I find it preferable that both pole pieces on each magnet structure "be adjustably movable, the methods of my invention can be obtained to some extent, at least, in structures; wherein only one pole piece is adjustably movable and the other stationary.

Additionally, the vernier field adjustment means described above can be applied to any magnet circuit and is not limited to employment with crossed field devices. Further, the pole pieces can be of any desired dimensions and configuration and need not include planar gapdefining', surfaces. For some applications it may be desirable to shape the pole pieces predeterminedly to provide for predetermined degrees of variation in the strength and shape of the field in the magnet gap.

While I have shown and described specific embodiments of my invention, I do not-desire my invention to be limited to the particular forms shown and described, and I intend by the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A11 electron discharge apparatus comprising in combination (a) a magnet structure,

(b) said magnet structure including oppositely spaced apart poles defining a gap therebetween and a magnetic field traversing said gap,

(c) at least one separate pole piece on one of said poles of said magnet,

(d) said separate pole piece having a surface defining an unobstructed gap with the other of said poles,

(e) an electron discharge device fixedly positioned in said gap in generally coaxial relationship with said magnetic field in said gap for operative interaction with said magnetic field,

(f) said separate pole piece being adjustably movable on said one pole so that its gap defining surface is moved to a different position with respect to concentricity with said other pole to alter the direction of the lines of force of said magnetic field through said electron discharge device,

(g) and means interconnecting said separate pole piece and said one pole to fixedly attach said pole piece in its adjusted position.

' 2. An electron discharge apparatus comprising in combination (a) a magnet structure,

(b) said magnet structure including oppositely spaced apart concentric poles defining a gap therebetween and a magnetic field traversing said gap,

(c) at least one separate pole piece on one of said poles of said magnet,

(d) said separate pole piece having a surface defining an unobstructed gap with the other of said poles,

(e) an electron discharge device fixedly positioned in said gap in generally coaxial relationship with said magnetic field in said gap for operative interaction with said magnetic field for electrical power output,

(f) said separate pole piece being adjustably movable on said one pole so that its gap defining surface moves to a position away from concentricity with respect to the other pole to alter the direction of the lines of force of said magnetic field through said electron discharge device,

(g) and bonding means bonding said separate pole piece to said magnet.

3. The invention as recited in claim 1 wherein said electron discharge device is a combination of a voltage tunable magnetron and a radio frequency circuit.

4. A unitary voltage tunable magnetron assembly comprising in combination (a) a magnet structure having a pair of opposed spaced apart concentric poles,

(b) said poles defining a gap therebetween traversed by a magnetic field from said magnet structure,

(c) a separate pole piece of a highly permeable magnetic material positioned on one of said pole pieces,

(d) a voltage tunable magnetron positioned coaxially between said pole piece and the other of said poles,

(e) a radio frequency circuit structure about and connected to said voltage tunable magnetron to fixedly position said magnetron with respect to said poles,

(f)' support means attached to said magnet and to said radio frequency structure to fixedly position said radio frequency structure coaxially between said pole piece and said pole,

(g) saidpole piece means to provide lateral movement with respect to its pole to alter the direction of the lines of force of the magnetic field through said voltage tunable magnetron,

(h) bonding means interconnecting said separate pole piece and said one pole to bond said pole piece in its moved position.

5. Apparatus comprising a magnet structure including a pair of spaced apart pole pieces positioned thereon, said pole pieces having opposed coextensive surfaces defining an unobstructed gap, means fixedly supporting an electric discharge device in a generally coaxial relation with a magnetic field in said gap, and at least one of said pole pieces being separate from said magnet and positioned thereon to be adjustably movable to various positions wherein its gap-defining surface extends in different oblique planes relative to the axis of said device for adjustively altering the configuration of said magnetic field in said device.

6. Radio frequency apparatus comprising a magnet structure including a yoke section and a pair of separate spaced pole pieces on yoke section having opposed un- Obstructed gap-defining coextensive surfaces, said pole pieces being of high permeability magnetic material. means fixedly supporting a crossed-field electricdischarge device including an interaction region andan axially into said interaction region in a generally coaxial p'ositionin a magnetic field in said gap and in spaced relation to said pole pieces, said separate pole pieces each being movable to various positions wherein said planar surfaces are disposed in various oblique planes relative to the axis of said device for adjustably varying the configuration of said magnetic field and thereby optimizing operation of said device.

References Cited by the Examiner UNITED STATES PATENTS Braden 315- 3911 x Ludi 315-4917 X Van Dorsten 250-495 Watson 317-4582 Helmer 317- -158 X Gang et al. 3l7,-158 2 

1. AN ELECTRON DISCHARGE APPARATUS COMPRISING IN COMBINATION (A) A MAGNET STRUCTURE, (B) SAID MAGNET STRUCTURE INCLUDING OPPOSITELY SPACED APART POLES DEFINING A GAP THEREBETWEEN AND A MAGNETIC FIELD TRAVERSING SAID GAP, (C) AT LEAST ONE SEPARATE POLE PIECE ON ONE OF SAID POLES OF SAID MAGNET, (D) SAID SEPARATE POLE PIECE HAVING A SURFACE DEFINING AN UNOBSTRUCTED GAP WITH THE OTHER OF SAID POLES, (E) AN ELECTRON DISCHARGE DEVICE FIXEDLY POSITIONED IN SAID GAP IN GENERALLY COAXIAL RELATIONSHIP WITH SAID MAGNETIC FIELD IN SAID GAP FOR OPERATIVE INTERACTION WITH SAID MAGNETIC FIELD, (F) SAID SEPARATE POLE PIECE BEING ADJUSTABLY MOVABLE ON SAID ONE POLE SO THAT ITS GAP DEFINING SURFACE IS MOVED TO A DIFFERENT POSITION WITH RESPECT TO CONCENTRICITY WITH SAID OTHER POLE TO ALTER THE DIRECTION OF THE LINES OF FORCE OF SAID MAGNETIC FIELD THROUGH SAID ELECTRON DISCHARGE DEVICE, (G) AND MEANS INTERCONNECTING SAID SEPARATE POLE PIECE AND SAID ONE POLE TO FIXEDLY ATTACH SAID POLE PIECE IN ITS ADJUSTED POSITION. 